1. Field of the Invention:
This invention relates to a thermopervaporation apparatus. More particularly, it relates to a thermopervaporation apparatus having a porous spacer positioned between a microporous membrane and a heattransmission wall to minimize the space therebetween thereby improving the yield of the condensate.
2. Description of the Prior Art:
As a method for separating water from an aqueous solution, there has been a thermopervaporation method wherein a feed solution such as brine is passed through one side of a microporous membrane (which is impervious to liquids while readily allowing the vapor to pass therethrough) and the vapor of the component to be separated from the feed solution is condensed on a cold wall at the other side of the membrane. A variety of apparatus for performing such a sparation method have been proposed. For example, Japanese Patent Publication No. 49-45461 (45461/1974) discloses a multistage thermopervaporation apparatus for separating a component from a solution by circulating the hot feed liquid to be distilled and a cooling liquid at respectively opposite sides of a gaseous region situated between the above-mentioned microporous membrane which is permeable to the vapor of the component to be separated and the cold wall on which that vapor is to condense, resulting in a pure water from brine.
Generally, such a thermopervaporation apparatus will be able to attain a high condensation rate for the vapor thereby attaining a high yield per hour of the condensate, and will be minimized if the space (i.e., a gaseous region) between the membrane and the cold wall is made small. However, the membrane is not rigid and tends to bend, so that it often comes into contact with the cold wall. The portion of the membrane which is in contact with the cold wall prevents not only the vapor from permeating the membrane but also the condensate from passing between the membrane and the cold wall, thereby reducing the yield of the condensate. Thus, a conventional thermopervaporation apparatus is constructed so that a large space between the microporous membrane and the cold wall is maintained to avoid contact therebetween. This accordingly results in an unavoidable reduction of the yield of the condensate.